I agree with Tonir, running in intervals is good. I'm not a total runner by any means but pushed myself to do a 10-mile race last year (I was definitly not a regular runner proir to it). Runners World has some cool things...I used the Smart Coach thing to get myself a personal training plan.
Runner's World: Running Shoes, Marathon Training, Racing
I would also recommend going to a running store and get fitted for a pair of running shoes. I went to one where they watched how your feet strike the ground when you run and walk, and picked a shoe for me that fit. I noticed a huge difference in my running after I got the right pair of shoes!